class_docstr: Note: call self.can_use() when arrays are already allocated, otherwise
  call self._test_can_use().
code: def tearDown(self):
      _accelerator.set_reduction_accelerators(self.old_accelerators)
  
imports: from itertools import combinations
  import unittest
  import sys
  import cupy
  from cupy import _environment
  from cupy import testing
  from cupy._core import _accelerator
  from cupy._core import _cub_reduction
  from cupy.cuda import memory
label_desc: Use image node_id 2 for calling the CubReductionTestBase obj's underlying member method code with example usage: obj.tearDown() without return types